%I A008509
%S A008509 1,2,3,10,11,18,34,36,77,109,132,173,363,1111,1287,1593,1833,2662,3185,
%T A008509 3369,3548,8382,11088,18906,50281,57166,102849,111111,167053,179158,
%U A008509 246642,337650,342270,365436,417972,1620621,3240425,3457634,3707883
%N A008509 Numbers n such that n-th triangular number is palindromic.
%D A008509 Charles W. Trigg, Palindromic Triangular Numbers, J. Rec. Math., 6 (1973), 
               146-147.
%D A008509 D. Wells, The Penguin Dictionary of Curious and Interesting Numbers. 
               Penguin Books, NY, 1986, 93.
%H A008509 P. De Geest, <a href="http://www.worldofnumbers.com/triangle.htm">Palindromic 
               Triangulars</a>
%Y A008509 Cf. A003098, A002113, A000217, A083571, A050721, A050722.
%Y A008509 Sequence in context: A081706 A032804 A047473 this_sequence A081868 A092986 
               A006092
%Y A008509 Adjacent sequences: A008506 A008507 A008508 this_sequence A008510 A008511 
               A008512
%K A008509 nonn,base
%O A008509 1,2
%A A008509 Patrick De Geest (pdg(AT)worldofnumbers.com)